Contact elements for surface mounting of burn-in socket

ABSTRACT

A circuit board assembly having a circuit board with at least one via, a pin for insertion into the via, and a contact element positioned adjacent to the pin and the via for providing electrical attachment of the pin to the via of the circuit board. The pin is detachable from the via and the contact element deforms upon insertion of the pin.

BACKGROUND OF THE INVENTION

[0001] The present invention concerns socket mounts, particularlyprinted circuit board contact elements used to mount electricaldevice-containing sockets to the circuit boards.

[0002] Burn-in sockets are generally soldered to the printed circuitboards. The solder electrically and mechanically secures the socket tothe printed circuit board.

[0003] Burn-in is a semiconductor industry manufacturing process forscreening out non-functional chips or devices. The chip is inserted intoa socket (commonly referred to as a burn-in socket), this socket holdsthe chip in place while providing electrical continuity from the chip toa printed circuit board (PCB).

[0004] The burn-in socket (BIS) comes with contact pins. The length ofthe contact pin that protrudes from the bottom of the socket into thePCB for soldering is called a solder-tail. When a socket is de-solderedfrom a PCB, solder remnants are left on the solder-tail. These solderremnants increase the diameter of the contact pin making it difficult toreuse the socket by inserting the increased diameter contact pin in anew board.

[0005] There are at least three problems associated with solderingsockets to the printed circuit board. First, in order to remove thesocket, the solder must be reheated. The reheating process may damagethe socket reducing its reliability when reused. In addition, thereheating process is difficult to limit to the area of the socket to beremoved, affecting adjacent sockets. Second, soldering may cause thermalstress which may lead to plastic deformation. Third, desoldering maycause solder bridging of solder remnants on the socket solder-tails.Solder remnants on the solder-tail also reduces the reliability if thesocket is replaced.

[0006] The number of contact pins per socket can range from as few as 10contact pins to 1500 or more contact pins. It is critical for thecontact pins to remain straight so that they align with the holes in thePCB. After the burn-in socket is removed from the PCB, the contact pinsmay become bent or misaligned due to reheating or solder remnants on thesocket solder-tail. Lastly, the cost of wave soldering equipment is highand processing lead times to replace a socket may be long.

[0007] Thus, there is a need for a socket mount that provides secureelectrical connectivity between sockets and printed circuit boardswithout damage caused to the socket and adjacent sockets by reheating ofsolder socket connections. There is also a need for a simplifiedmounting and removal process for sockets that reduces the long leadtimes encountered with soldering operations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIGS. 1 and 2 are side views of one embodiment of a printedcircuit board assembly depicting two sockets, FIG. 1 depicts a socketmounted to the circuit board with its pins received in contact elementsconfigured in conformance with the principles of the present inventionand FIG. 2 depicts a socket not yet mounted to a circuit board.

[0009]FIG. 3 is a side view of one embodiment of a printed circuit boardassembly depicting mounting the contact elements on the bottom side ofthe printed circuit board instead of between the printed circuit boardand the socket as shown in FIGS. 1 and 2.

[0010]FIG. 4 is a magnified top view of one embodiment of a contactelement.

[0011]FIG. 5 is a side view of the contact element of FIG. 4.

[0012]FIG. 6 is a magnified cross sectional side view of plating layersof one embodiment of a contact element.

[0013]FIG. 7 is a magnified top view of another embodiment of a contactelement.

[0014]FIG. 8 is a magnified top view of another embodiment of a contactelement.

[0015]FIG. 9 is an exploded perspective view of a contact element sheetand a circuit board depicting alignment of the contact elements withvias of the circuit board.

[0016]FIG. 10 is a side view of the circuit board and contact elementsheet depicting alignment of the alignment pin holes of the contactelement sheet and the alignment pin holes of the circuit board.

[0017]FIG. 11 is a side view of the circuit board assembly depictingalignment of the circuit board and the contact element sheet, andalignment of the circuit board and the socket.

[0018]FIG. 12 is a side view of an embodiment of an assembled circuitboard assembly.

[0019]FIG. 13 is a side view of one embodiment of a disassembled circuitboard assembly depicting used contact elements.

[0020]FIGS. 14 and 15 are magnified side views showing the insertion ofanother embodiment of a contact element into the via of the circuitboard.

[0021]FIGS. 16 and 17 are magnified side views of the inserted contactelement of FIGS. 14 and 15 receiving a socket pin.

[0022]FIG. 18 is a perspective view of another embodiment of a contactelement.

DETAILED DESCRIPTION

[0023] In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which are shownby way of illustration specific embodiments in which the invention maybe practiced. It is to be understood that other embodiments may beutilized and structural changes may be made without departing from thescope of the present invention.

[0024] To address these needs, one exemplary embodiment of a printedcircuit board assembly includes a printed circuit board, a socket havinga pin, and a contact element securing the pin to the printed circuitboard.

[0025] Advantageously, the socket may be removed without damaging thesocket or adjacent sockets. The socket is removably secured to theprinted circuit board without the use of solder.

[0026]FIG. 1 shows an exemplary circuit board assembly 10. The assembly10 includes a circuit board 20 having at least one via 22. The circuitboard 20 will ultimately be electrically connected to a device or chip31 under test held in a burn-in socket 30 with at least one pin 32carried by the socket 30. A contact element 40 provides electricalcontinuity between the pin 32 of the burn-in socket 30 and the via 22 ofthe circuit board 20. Solder paste 50, is optionally used to improve theelectrical connection between the contact 40 and the circuit board 20.

[0027]FIG. 2 shows circuit board assembly 10 with the pins 32 of theburn-in socket 30 disconnected from the circuit board 20.

[0028] A number of contact elements 40 are inserted or attached to eachvia 22 of circuit board 20 to mate with a pin grid array of pins 32 ofthe burn-in socket 30. Burn-in socket 30 is attachable to and removablefrom the circuit board 20 without subjecting the circuit board assembly10 to wave soldering. No soldering is required to secure electricalconnectivity between the socket pins and the burn-in socket, as will bedescribed in detail below. Mounting and removal processes of the burn-insocket are simplified. No heat is needed to remove the burn-in socketfrom the circuit board. The burn-in socket 30 is also secured to thecircuit board 20 by using fasteners 60. The burn-in sockets 30 may beused in conjunction with another circuit board. Since no solderingequipment is necessary, shorter replacement times are possible. Inaddition, individual, damaged, or defective burn-in sockets are easilyreplaceable without affecting adjacent areas of the circuit board 20.

[0029]FIG. 3 shows another embodiment of circuit board assembly 110 withthe contact element 40 located beneath the printed circuit board 20instead of between the printed circuit board and the burn-in socket asshown in FIGS. 1 and 2. Optionally, a contact element sheet 70 positionsthe contact elements 40 for receiving the pins 32. The contact elementsheet 70 is a high temperature resistant adhesive sheet, for example,but not limited to KAPTON tape, for securing the contacts 40 inposition.

[0030] Referring to FIGS. 4 and 5, contact element 40 a is a disk 49with large cuts 41, small cuts 42, and grooves 43 formed in the disk 49to provide an opening for a contact pin to pass through. The disk 49 maybe formed from a plated metal sheet 80 as further described in FIG. 6.The disk 49 is shown as but not limited to a circular shape, othershapes such as square or rectangular for example may also be used. Fourlarge cuts 41 meet at the center of the disc 49, forming a cross. Asmall cut 42 is located at each end of the cross, forming a T shape outof each of four legs of the cross. The base of each of the T shapes meetat the center of the disk 49 and forms four fingers 44. Optionally,grooves 43 are formed at the point where the fingers 44 connect to thecircular disk 49 between the top outer ends of each of the T shapes.Grooves 43 are channels formed in one side of the disk 49 that do notpass all the way through the disk 49. The grooves 43 reduce the forceneeded to deflect fingers 44 as the pin is inserted through the contactelement 40 a.

[0031] As shown in FIG. 6, the plated metal sheet 80 is comprised of,but not limited to a base 82 of Beryllium Copper (BeCu) with a insidelayer 84 of nickel (Ni) and an outside layer 86 of gold (Au).

[0032]FIGS. 7 and 8 show additional embodiments of a contact element 40.FIG. 7 depicts contact element 40 b formed from a disk 49 with a roundcut 45 and a plurality of extension cuts 46 formed in a circular shapeddisk. Optionally, grooves 43 are formed in the disk 49 between theextension cuts 46. FIG. 8 depicts contact element 40 c formed from adisk 49 with a round cut 45 and a plurality of extension cuts 46 formedin the circular shaped disk. Optionally, grooves 43 are formed in thedisk 49 between the extension cuts 46.

[0033] As shown in FIG. 9, a circuit board 20 with an array of vias 22aligns with a contact element sheet 70 with an array of contact elements40. The vias 22 and contact elements 40 are aligned using alignment pinholes 72 in the circuit board 20 that match with alignment pin holes 72in the contact element sheet 70.

[0034] As shown in FIG. 10, a cross sectional view of the contactelement sheet 70 and contact elements 40 positioned adjacent to andaligned with the circuit board 20 using the alignment pin holes 72.Optionally, solder paste 50 is positioned on the contact elements 40,however, the solder paste 50 may also be placed on the circuit board 20prior to positioning the contact elements 40 on the circuit board 20.

[0035]FIG. 11 shows the circuit board assembly 10 aligned for assembly.The alignment pin holes 72 of the contact element sheet 70 align withthe alignment pin holes 72 of the circuit board 20. The socket pins 32align with the vias 22 in the circuit board 20.

[0036]FIG. 12 shows an assembled circuit board assembly 10. The pins 32are inserted in the vias 22 and the fingers 44 of the contact elements40 are displaced to allow passage of the pin 32 through the contactelement 40. The contact element 40 provides electrical and mechanicalcontinuity between the pins 32 and the via 22 of the circuit board20.The fingers 44 are forced open as the pin 32 is inserted. The springeffect or resiliency of the contact element 40 provides frictionalcontact and electrical contact between the contact element 40 and pin32. The fingers 44 may assume a first inside diameter 46 and a secondinside diameter 47. The first inside diameter 46 of the fingers 44 isless than the diameter of the pin 32. The second inside diameter 47 ofthe fingers 44 is substantially equal to the diameter of the pin 32. Thesocket 30 is secured to the circuit board 20 with a fastener 60.

[0037] The circuit board assembly 10 includes a circuit board 20 havingat least one via 22. The circuit board 20 electrically connects to aburn-in socket 30 with at least one pin 32. A contact element 40provides electrical continuity between the pin 32 of the burn-in socket30 and the via 22 of the circuit board 20. Optionally, a number ofcontact elements 40 are inserted or attached to each via 22 of circuitboard 20 to mate with a pin grid array of pins 32 of the burn-in socket30. Burn-in socket 30 is attachable and removable from the circuit board20 without subjecting the circuit board assembly 10 to wave soldering.No soldering is required to secure electrical connectivity between thesocket pins 32 and the circuit board 20. Mounting and removal processesof the burn-in socket 30 are simplified. No heat is needed to remove theburn-in socket 30. The burn-in socket 30 is also secured to the circuitboard 20 by using at least one fastener 60. The burn-in socket 30 may beused on another circuit board with a new set of contact elements. Sinceno soldering equipment is necessary, shorter replacement times arepossible. In addition, individual, damaged, or defective burn-in socketsare easily replaceable without affecting adjacent areas of the circuitboard 20.

[0038]FIG. 13 shows the circuit board assembly 10 disassembled. Thesocket 30 may be removed from the circuit board 20 without heating thecircuit board 20 or the use of wave solder equipment. The fastener 60 isremoved and the socket 30 is released from circuit board 20. The contactelements 40 deform to release the pins 32 from the contact elements 40.

[0039] As shown in FIGS. 14-17, another embodiment of contact element 40c is press fit into the via 22 of the circuit board 20. The outsidediameter of the contact element 40 c is substantially equal to thediameter of the via 22 so that the contact element 40 c is press fitinto the via 22. Press fitting the contact element 40 c into the via 22provides electrical and mechanical contact between the via 22 and thecontact element 40 c.

[0040] As shown in FIG. 16, pin 32 is inserted through contact element40 c forcing the fingers 44 of contact element 40 c to spread apart. Thespring effect or resiliency of the contact element 40 c providesfrictional contact and electrical contact between the contact element 40c and pin 32.

[0041] The plurality of fingers 44 have a first inside diameter 46 asshown in FIG. 16 and a second inside diameter 47 as shown in FIG. 17.The first inside diameter 46 of the plurality of fingers 44 is less thanthe diameter of the pin 32. The second inside diameter 47 of theplurality of fingers 44 is substantially equal to the diameter of thepin 32.

[0042] As shown in FIGS. 14-17, the contact element 40 c includes a lipportion 91 and a tapered portion 92. The lip portion 91 has an outsidediameter greater than an inside diameter of a via 22 and an openinggreater than the outside diameter of a pin 32. The tapered portion 92has an outside diameter less than the inside diameter of the via 22 anda first inside diameter 46 less than the outside diameter of the pin 32.The tapered portion 92 is deformable, such that upon insertion of thepin 32, the tapered portion 92 is deflectable to a second insidediameter 47 substantially equal to the outside diameter of the pin 32.

[0043] An additional embodiment of contact element 40 is shown in FIG.18. It shows contact element 40d with a plurality of fingers 44. Thesefingers 44 are inwardly extending fingers 86. The plurality of fingers44 deflect to provide a first inside diameter 46 and a second insidediameter 47. The first inside diameter 46 of the plurality of fingers isless than the diameter of the pin 32. The second inside diameter 47 ofthe plurality of fingers 44 is substantially equal to the diameter ofthe pin 32. The spring effect or resiliency of the contact element 40 dprovides frictional contact and electrical contact between the contactelement 40 d and pin 32.

[0044] As shown in FIGS. 18, the contact element 40 d includes a baseportion 93 and a plurality of fingers 44. The base portion 93 has anoutside diameter greater than the inside diameter of the via 22 and thebase portion 93 has an opening greater than the outside diameter of thepin 32. The plurality of fingers 44 form a first inside diameter lessthan the outside diameter of a pin 32. The plurality of fingers 44 aredeformable, such that upon insertion of the pin 32, the plurality offingers 44 are deflectable to a second inside diameter substantiallyequal to the outside diameter of the pin 32.

[0045] Alternatively, the contact element can be attached to the via byinfrared reflow. An exemplary method of securing a pin to a via in acircuit board includes placing a contact element adjacent to the via,inserting the pin through the contact element, deforming the contactelement, and providing an electrical and mechanical connection betweenthe pin and the via with the contact element.

[0046] Optionally, the method includes removing the pin from the viawithout heating the pin and via.

[0047] Advantageously, the circuit board assembly provides a contactelement that allows the socket to be removed from the printed circuitboard without damaging the socket, adjacent sockets, or the printedcircuit board. The socket is removably secured to the printed circuitboard with a replaceable contact element without the use of solder.

[0048] It is to be understood that the above description is intended tobe illustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A circuit board assembly comprising: a circuitboard having a via; a pin for insertion into the via; a contact elementpositioned adjacent to the pin and the via for providing electricalattachment of the pin to the via of the circuit board; wherein the pinis detachable from the via; wherein the contact element deforms uponinsertion of the pin.
 2. The circuit board assembly of claim 1 whereinthe pin is attached to the circuit board without solder.
 3. The circuitboard assembly of claim 1 wherein the contact element is electricallyattached to the pin and the via by press fitting the contact element inthe via and inserting the pin in the contact element.
 4. The circuitboard assembly of claim 1 wherein the contact element is electricallyattached to the pin and the via by infrared reflow.
 5. The circuit boardassembly of claim 1 wherein the contact element is attached to a firstside of the circuit board and the pin is inserted from a second side ofthe circuit board.
 6. The circuit assembly of claim 1 wherein thecontact element has a plurality of fingers.
 7. The circuit assembly ofclaim 1 wherein the contact element has a plurality of inwardlyextending fingers.
 8. The circuit assembly of claim 1 wherein thecontact element has a plurality of outwardly extending fingers.
 9. Thecircuit assembly of claim 1 wherein the contact element has a pluralityof inwardly extending fingers and a plurality of outwardly extendingfingers.
 10. A contact element comprising: a plated disk having aplurality of cuts defining a plurality of fingers; the fingers adaptedto be received within a via, the plated disk defining an opening forreceiving a pin, the fingers having a first inside diameter less thanthe outside diameter of a pin; wherein the fingers are deformable, suchthat upon insertion of the pin, the fingers are deflectable to a secondinside diameter substantially equal to the outside diameter of the pin.11. The contact element of claim 10 wherein the contact element providesan electrical and mechanical contact between the pin and the via. 12.The contact element of claim 10 wherein the plated disk has at least onegroove defined between the cuts.
 13. The contact element of claim 10wherein the plated disk has a round cut and extension cuts.
 14. Acontact element comprising: a disk and a plurality of fingers; the diskhaving an outside diameter greater than an inside diameter of a via, thedisk having an opening greater than an outside diameter of a pin, theplurality of fingers forming a first inside diameter less than theoutside diameter of a pin; wherein the plurality of fingers aredeformable, such that upon insertion of the pin, the plurality offingers are deflectable to a second inside diameter substantially equalto the outside diameter of the pin.
 15. The contact element of claim 14wherein the contact element provides an electrical and mechanicalcontact between the pin and the via.
 16. The contact element of claim 14wherein the contact element is formed from a sheet of plated metal. 17.The contact element of claim 14 wherein the plurality of fingerscomprise inwardly extending fingers.
 18. The contact element of claim 14wherein the plurality of fingers comprise outwardly extending fingers.19. The contact element of claim 14 wherein the contact element issecured to the pin using infrared reflow.
 20. A contact element whichfacilitates the mechanical and electrical mounting of an electricaldevice-carrying socket, the socket bearing one or more pins, to acircuit board having one or more conductive vias, the contact elementcomprising: an electrically conductive body having external surfacefeatures rendering the body removably attachable to the via, the bodydefining a pin-receiving portion, and surface features of the body onthe pin receiving portion, the features resiliently engaging a receivedpin to effect electrical and mechanical engagement between the contactelement and the pin.
 21. The contact element of claim 20 furthercomprising a lip portion and a tapered portion; the lip portion havingan outside diameter greater than an inside diameter of a via, the lipportion having an opening greater than an outside diameter of a pin, thetapered portion having an outside diameter less than the inside diameterof the via and a first inside diameter less than the outside diameter ofa pin; wherein the tapered portion is deformable, such that uponinsertion of the pin, the tapered portion is deflectable to a secondinside diameter substantially equal to the outside diameter of the pin.22. The contact element of claim 20 further comprising: a base portionand a plurality of fingers; the base portion having an outside diametergreater than an inside diameter of a via, the base portion having anopening greater than an outside diameter of a pin, the plurality offingers forming a first inside diameter less than the outside diameterof a pin; wherein the plurality of fingers are deformable, such thatupon insertion of the pin, the plurality of fingers are deflectable to asecond inside diameter substantially equal to the outside diameter ofthe pin.
 23. A method of securing a pin to a via in a circuit boardcomprising placing a contact element adjacent to the via; inserting thepin through the contact element; deforming the contact element;providing an electrical and mechanical connection between the pin andthe via with the contact element.
 24. The method of claim 23 furthercomprising removing the pin from the via without heating the pin andvia.
 25. The method of claim 23 wherein providing an electrical andmechanical connection comprises infrared reflow.